This invention relates to crawler vehicles and more particularly to track chain suspensions therefor.
The track chain of most commercial crawler vehicles is usually engaged on a pair of large longitudinally spaced wheels wherein the forward wheel is an idler and the rear wheel is toothed and constitutes the drive sprocket for the chain; smaller roller wheels being distributed between the two major wheels for support and load bearing purposes. A disadvantage of such a configuration is the long track frame carrying the wheels. Such a long frame enhances vertical displacements of the track chain suspension mechanisms when driving on rough terrain. For use on concrete laying machines it is however important that shock and drive load forces on the vehicle are maximally reduced and/or prevented. Present solutions to provide for the absorption of shocks and to provide for maintenance of track chain tension and vehicle stability consist of triangular track chain suspensions such as for example described in U.S. Pat. No. 3,841,424. In such triangular track chain suspensions the drive train is moved upward and above the track frame carrying the idlers and track rollers. Shortening the base with an eventual pivotal connection, results in a resilient drive train having recoiling ability with an increased absorption of shocks and efficient driving action on rough terrain.
Where suitable for certain crawling devices, such triangular track chain suspension mechanisms are not suitable for machines that have to pull heavy loads such as machines for laying concrete paths of the type in which a concrete mix in the plastic state is spread over a certain width and levelled by means of a levelling element suspended behind the machine. In such machines very high leverage forces are acting on the drive shaft of the track chain suspension mechanisms. With a triangular configuration the elevated drive shaft lengthens the load arm and front lifting of the vehicle can hardly be prevented, in particular when driving over rough terrain where vertical displacements of the track frame due to relief elements add to the leverage forces acting on the drive shaft when pulling heavy loads.
It is an objective to address the foregoing problems and to provide track chain suspension mechanisms, which provide for a smooth and levelled operation of the vehicle, in particular for machines that have to pull heavy loads such as machines for laying concrete paths of the type in which a concrete mix in the plastic state is spread over a certain width and levelled by means of a levelling element suspended behind the machine.